How to configure Blender for 2D functions only?
You want to setup the layout the way you want and save it as his startup.blend.

By adjusting his preferences you can delete entries for changing orthographic/perspective, view front/top/right. As you probably know the shortcuts you want to disable you can search for the inputs by key-binding.

The far extreme is to compile a custom build for him, with this you can also remove menu entries for changing the view orthographic/perspective and even hide the window types menu so he can't accidentally change the 3dview to something else.

Or you can just teach him to use what he needs, and say just ignore all the other stuff that you don't need to use. I'm sure he can handle exploring other parts of blender if he feels adventurous and knows you to call when he gets lost.